Create kernel character module and oops information understanding

Simply record the positioning steps of the Linux Oops. First create a demo, this demo is to create a character device demo.

First, create the code of demo module

# include # define MINOR_BASE 0#define COUNT_NUM 3static struct cdev * cdevp = NULL;static dev_t dev;struct class * demo_class = NULL;struct device * drv_device;int demo_open (struct inode * node, struct file * filp) {printk (KERN_INFO "% s% d demo_open called...\ n", _ _ func__,__LINE__); int * p = NULL;*p = 1; / * null pointer assignment * / return 0 } int demo_release (struct inode * node, struct file * filp) {printk (KERN_INFO "% s% d demo_release called...\ n", _ _ func__,__LINE__); return 0;} ssize_t demo_read (struct file * filep, char _ _ user * user, size_t size, loff_t * loffp) {printk (KERN_INFO "% s% d demo_read called...\ n", _ _ func__,__LINE__); return 0 } ssize_t demo_write (struct file * filep, const char _ user * user, size_t size, loff_t * loffp) {printk (KERN_INFO "% s% d demo_write called...\ n", _ _ func__,__LINE__); return size;} struct file_operations opfp = {.owner = THIS_MODULE, .open = demo_open, .release = demo_release, .read = demo_read, .write = demo_write,} Static int _ init demo_init (void) {int ret; / / dev_t ret = alloc_chrdev_region (& dev,MINOR_BASE,COUNT_NUM, "cdev_demo"); if (ret